In nonvolatile memory such as flash memory, the sector erase operation is performed on memory cells by applying a global word line voltage to a memory sector to be erased.
Conventionally, if the global word line voltage is at a negative level, all local word lines of the memory sector will be set to an erased status. In such configuration, the number of needed global word lines directly depends on the size of the sector unit. That is, when the sector unit size becomes more less, the needed global word line number will be more. However, the increment of needed global word line number will increase the total circuit area.